Electron discharge device



Aug. 9, 1966 J. P. MACDONELL ETAL 3,265,921

1 ELECTRON DISCHARGE DEVICE Filed July 13, 1962 Fig.l.

WITNESSES v INVENTORS Jam-es P Mocdonell 8 Douglas G. Noiles United States Patent 3,265,921 ELECTRON DISQHARGE DEVTCE James P. Macdouell and Douglas G. Noiles, Bath, N.Y., assignors to WestinghouseElectric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed July 13, 1962, Ser. No. 2ii9, 9 4 Claims. (Cl. 313-492) This invention relates to electron discharge devices and more particularly to the construction and mounting of electrodes for such a device.

In some electron discharge devices, such as receiving tubes, the electrode elements of the cage assembly are mounted between spaced insulating members or sheets of a suitable material such as mica. The characteristics of the electron discharge devices depend on the size of the electrodes and the spacing of the electrodes within the cage assembly. It is therefore necessary in most receiving tube types that the electrode elements must be made very small. The spacing and uniformity of the electrode elements must be closely controlled for the operating characteristics of a particular tube type to prevent variation of characteristics from tube to tube. It is also obvious that those tubes which do not meet certain requirements are rejected. This increases the manufacturing cost of the tube. It is desirable to design the electrode components of the electron cage of adequate mechanical strength to Withstand handling and in addition be of simple construction and provide ease in assembly to provide uniform tube characteristics throughout one tube type.

In one particular receiving tube type, namely the BB6, the second grid from the cathode is provided with two curved strip shield members spot welded to the second grid assembly. In this prior art type structure, the curved shields are normally stamped from strip stock. This type of construction results in inherent lack of control over the geometrical shape of the part. It is also found that the stamped part may have a camber in either direction which results in a bow in the grid side rods and distortion in the grid. In addition, the strip shields may have a twist along their length which results in twisting of the grid after the grid strips are secured to the grid electrode. It is important in this tube type that the gap between the shields through which the electrons flow be centralized with respect to the grid and in addition the gap should be of constant width. The width of the gap or aperture between the shield strips and the centrality of the major axis vary with the degree of radial symmetry of the two shield members. It is found in the prior art device that the aperture may have a variance in width along its length as well as a difference in width on opposite sides of the grid and the aperture will normally not be centralized with respect to the grid. Even if the parts are symmetrical, there is still the problem associated with the welding operator in aligning the two shield strips before welding to the grid. It is also possible that the edges of the strips may come in contact with the lateral Wire portion of the grid which results in damage to the laterals during the welding process.

Another problem is the alignment of the shields along the length of the grid legs which again may vary with operators skill. One grid shield strip may have more of the grid leg exposed at one end than does the other grid shield strip. This structure hampers proper spacing between the top and bottom mica spacers in the finished Icage assembly and will distort the grid laterals if an attempt is made to seat both shields against one of the mica spacers. This will destroy the uniform spacing between the grid laterals as well as possibly damage the laterals themselves. Although it is possible to manufacture the tube using separate shields, it is found that the manufac- 3,2653% Patented August 9, 1966 turing techniques necessary to provide a quality product are not economical in large volume production.

It is therefore an object of this invention to provide an improvedelectron discharge device.

It is another object of this invention to provide an improved electrode construction to facilitate the manufacture of the electrode.

It is another object of the invention to provide an improved electrode assembly wherein a grid type electrode has shielding strips mechanically and electrically secured to the side rods to provide alignment of these strips with respect to the grid.

It is another object of this invention to provide an improved electrode construction to eliminate distortion of elongated shield strips which are attached to electrode elements within an electron cage.

Briefly, the present invention accomplishes the abovecited objects by providing an integrated one-piece shield structure. The one-piece structure includes two shield strips with a top and lower connecting cross piece on one side which defines one aperture. The gap on the other or open side of the shield is designed to be of the same Width as the aperture provided on the other side. This one-piece shield structure may be precision formed and can be held within geometrical tolerances. The structure removes any camber and twists within the two shield strips. The symmetry of the device is assured by the nature of the design. The window'which is punched in one side of the shield determines the opening gap through which the electrons flow while the gap on the other side or open side of the shield is designed with the same width. The part is spot welded to the grid side rods. The finished assembly presents a controllable, symmetrical, uniform and rigid structure. The unitized shield also provides a cost saving in labor content since only one part must be handled. The ross pieces at the top and bottom of the grid structure also protect the grid laterals from being pushed or damaged and thereby increases the structural strength of the grid assembly. The structure also insures that there will be similar spacing between the end of the side rods and the shield at one end of the grid.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIGURE 1 is an enlarged fragmentary, partially broken-away, perspective illustration of an electron discharge device incorporating our invention;

FIG. 2 is a cross-section view of the device of FIG. 1 taken on the line II-II;

FIG. 3 illustrates an enlarged partially broken-away perspective view of one of the grid electrodes illustrated in FIG. 1; and

FIG. 4 is a cross-section plan view of the assembly shown in FIG. 3 taken on the line VI-VI.

Referring to FIG. 1, there is shown an electronic tube of the BB6 type. The tube, generally designated 16*, including an envelope 12 containing an electrode mount or cage assembly, generally designated 14. The tube 10 includes a base portion (not shown) with a plurality of terminal pins projecting into the envelope for connecting the electrodes in the cage assembly 14 to external circuitry.

The electrode cage 14 includes a pair of spaced insulator discs or spacer members 16 of a suitable material such as mica. The spacers 16 include circumferentially spaced projections 18 for engaging the side walls of the envelope 12 to assist in positioning the electrode cage 14 within the envelope 12. The spacers 16 are each formed to include a plurality of apertures 20 adapted for fitting portions of the electrode elements of the cage assembly 14 therein, as illustrated. A centrally disposed aperture 2% is provided within each of the spacers 15 for receiving the end portions of a cathode 22 to thereby mount the cathode 22 in the cage 14. The cathode 22 is of la suitable indirectly heated type. The cathode 22 consists of a tubular sleeve with an electron emissive coating on the outer surface and a heater within the sleeve. A first grid electrode 24 surrounds the cathode 22. The first grid 24 consists of two support rods and lateral wire wound about the support rods. The end portions of the support rods of the grid 24 are secured in openings in the spacers 16 to mount the grid 24 in the cage 14. A second grid 26 surrounds the first grid and consists of two support rods 40 and 41 with a lateral wire 42 wound about the side rods 40 and 41 as clearly illustrated in FIGS. 3 and 4. A grid shield assembly 50 is secured to the side rods 40 and 41. The end portions of side rods 49 and 41 are positioned in apertures provided in the spacers 16. The ends of a shield assembly b are also positioned against the inner surface of the spacers 16 as illustrated in FIG. 1.

A third, fourth and fifth grid 28, 30 and 32, respectively, surround the second grid 26 and are mounted within the cage 14 in a similar manner as the first grid 24.

An anode 34 surrounds the grid electrodes and is provided with ears 35 that pass through openings provided in the spacers 16. The ears 35 are bent over and the cage assembly 14 is thereby locked together.

It is clear from the drawing that the various electrodes 22, 24, 26, 28, 30, 32 and 34 are coaxially arranged in closely spaced relationship and are adapted for being mounted by the end portions of the electrodes through the insulating spacer members 16. The electron discharge device illustrated here is substantially a conventional BB6 type structure with the exception of grid assembly 26. The prior art type control grid assembly has previously been discussed and consists essentially of a conventional grid structure with two shield strips welded along the side rods.

Referring now in detail to FIGS. 3 and 4, there is shown the grid electrode assembly 26 which includes the two side rod members elt and 41 of a suitable material, such as nickel plated iron. The side rod members have a diameter of about .025 inch. The lateral wire 42 is helically wound about the two side rod members 40 and 4-1 by any conventional means, such as the rotary grid winding machine, and the resulting grid 25 has an elliptical cross section, as illustrated in FIG. 4. The grid shield assembly 56 also has a generally elliptical cross section and consists of two elongated curved grid strips 52 and 54 which may be considered to be part of an ellipse with a top and lower cross piece 56 and 58, respectively. The grid strip member is normally fabricated of a suitable material, such as nickel plated steel, having a thickness of about .005 inch. The normal fabrication technique is to stamp this part out of a flat strip and then form the member by conventional techniques into the shape illustrated. The width of a window 66 formed by the two grid strips 52 and 54 and the two cross pieces 56 and 58 is of the same dimension as the spacing as between the opposed edges on theother side of the grid strip member and forming an opening 62. The inside long dimension of the elliptical grid shield 50 is such that the distance between the central portions of the two grid strips 52 and 54 is substantially equal to the long dimension of the wound grid portion. The assembly Slit may easily he slipped over the wound grid portion 25 and secured thereto by welding, as illustrated in FIGS. 3 and 4-. The short dimension of the grid shield assembly 59 is such as to provide adequate clearance from the turns of the lateral 42 so that there is no danger of contact of the opposed edges of the shield member portions 52 and 54 with the laterals of the grid 25 nor of the cross pieces 56 and 58 with the lateral wire 42. The portion of the side rods 40 and 41 extending above and below the grid shield 50 are inserted into apertures provided in the spacer members 16. The ends of the grid shield 50 are in physical contact with the spacers 16 to provide a rigid structure.

While there has been shown and described what is at present considered to be the preferred embodiment of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangement shown and described and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

We claim as our invention:

1. An electron discharge device comprising at least a cathode, a grid and an anode, said grid comprising two parallel side rods having lateral wires wound about said side rods, a shield member secured to said grid, said shield member comprised of two spaced apart curved portions attached to said side rods respectively along their length and a pair of connecting members secured to said curved portions on only one side.

2. An electron discharge device comprising a cathode having a tubular sleeve, a grid electrode surrounding said cathode, said grid provided with parallel side rods having lateral wires wound about said side rods, the side rods of said grid lying in a plane containing the longitudinal axis of said cathode, an anode spaced from said cathode for collecting the electrons emitted from said cathode, a pair of spaced apart, oppositely disposed U-shaped channel shield members attached to said side rods respectively along their length, the opposed edges of said channel members lying in parallel planes and spaced from said cathode to define two openings to provide two paths for electrons from the cathode to the anode and connecting members positioned at the top and bottom of only one of the openings connecting the opposed edges of said channel members.

3. An electron discharge device comprising a thermionic cathode, grid surrounding said cathode, said grid provided with two parallel support side rods having lateral wires wound about said side rods, concave opposing shield members attached mechanically and electrically respectively to said side rods with the opposed edges of said shield members parallel to said side rods, opposed edges of said shield forming between them two openings through which electrons travel from said cathode to said anode and members connecting only the opposed edges defining one of said openings.

4. An electron dis-charge device comprising at least a cathode, a control electrode and an anode, said control electrode comprising two parallel side rods having lateral wires wound about said side rods, a shield member secured to said control grid, said shield member comprised of two spaced apart concave opposed portions secured respectively to said side rods and a pair of integral connecting portions securing said concave portions together on only one side.

References Cited by the Examiner UNITED STATES PATENTS 1,696,103 12/1928 Seibt 313-299 2,837,673 6/1958 Quigley et 'al. 313-298 X 2,860,273 11/1958 OFallon 313299 JOHN W. HUCKERT, Primary Examiner. JAMES D. KALLAM, Examiner. 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AT LEAST A CATHODE, A GRID AND AN ANODE, SAID GRID COMPRISING TWO PARALLEL SIDE RODS HAVING LATERAL WIRES WOUND ABOUT SAID SIDE RODS, A SHIELD MEMBER SECURED TO SAID GRID, SAID SHIELD MEMBER COMPRISED OF TWO SPACED APART CURVED PORTIONS ATTACHED TO SAID SIDE RODS RESPECTIVELY ALONG THEIR LENGTH AND A PAIR OF CONNECTING MEMBERS SECURED TO SAID CURVED PORTIONS ON ONLY ONE SIDE. 